Description

EDIT: In 18w48b it's still possible to power through pistons, as demonstrated in this video provided by MethodZz: https://streamable.com/yi6fc

In 18w45a and prior, pistons are transparent, meaning they don't conduct redstone power and they won't cut off redstone signals.

In 18w46a, however, this changed. As can be seen in the attached screenshots, they now cut off redstone signals and it's possible to power through them. This breaks existing contraptions and also introduces new problems (3rd screenshot. Whether the front or back piston extends is seemingly random).